Sounds like the CDI box is fine then. It's most likely a relay! In the rear left of the engine bay, there's a black cover, remove this and there are some relays and fuses. The black round relay there can sometimes work loose, it did it on mine once and i had to get it towed 300 miles. The other relays are in the front, once you have the lead disconnected from the back of the fuel head/metering plate assembly, and the ignition is on and the lights are up on the dash, you sholuld be able to clearly hear both pumps running, it's a good time to listen and see if they sound healthy too. If the pumps aren't running just play with the relays, swap them around etc, it'll be clear which the dodgy one is. Also a good time to order a couple of spares!